Abstract: System and methods are disclosed for collecting detailed list of frequencies along with any relevant information such as users, time of day, weather, ionospheric conditions, quality of the transmission. This information is used to create a detailed frequency map. The frequency map is continuously updated. The frequency map is used to generate an optimum list of frequency bands that can be used for frequency sharing. Having a real-time frequency map allows for fast and reliable switching between optimum frequencies if a primary user is detected during transmission.

Abstract: System and methods are disclosed for collecting detailed list of frequencies along with any relevant information such as users, time of day, weather, ionospheric conditions, quality of the transmission. This information is used to create a detailed frequency map. The frequency map is continuously updated. The frequency map is used to generate an optimum list of frequency bands that can be used for frequency sharing. Having a real-time frequency map allows for fast and reliable switching between optimum frequencies if a primary user is detected during transmission.

Abstract: System and methods enabling radio communications that are operating in noisy environments using OFDM (Orthogonal Frequency Division Multiplexing) are disclosed. A spread OFDM transmitter that generates OFDM symbols that may include multiple copies of IFFT symbols is disclosed. A spread OFDM receiver is disclosed for receiving the spread OFDM symbols. Other methods for symbol detection, frequency offset correction, and equalization are disclosed.